Power tools and other portable electrical equipment are generally equipped with a relatively short electrical power cord having a male plug at the end thereof. However, a longer power cord is often required to provide power to the tools in an area remotely located from an electrical outlet. As a result, power tools are frequently connected to remote outlets via extension cords. An extension cord is an electric cord fitted with a male plug at one end and a female receptacle at the other end. The female receptacle end of the extension cord is mated with the male plug of the power tool cord. The male plug of the extension cord is inserted into a conventional outlet, providing an electrical connection between the outlet and the power tool. Additionally, numerous extension cords may be connected together, extending the distance of the electrical connection between power tools and remote outlets.
Electrical cords maintain a plugged together relationship between prongs of the male plug and corresponding receptacles of the female plug through friction. The friction between the plugs is adequate to maintain the electrical cords in a plugged together relationship when the cords are stationary. However, the friction between plugs may be insufficient to hold the electrical cords together when the cords are moved around, such as at a construction site. In the latter situation, the insufficient friction between the plugs causes them to accidentally separate, interrupting the flow of electricity to the power tool. The interruption of the flow of electricity to the tool can be annoying and time consuming, and sometimes possibly dangerous in certain situations.
Therefore, there are severl types of cord lock which are applied, such as U.S. Pat. No. 5,582,524 as shown in FIG. 1 which is a perspective view of an embodiment for an invention, wherein there are two eyelet members provided on a base member, and two planar brims provided between two eyelet members, the electrical cord behind male plug and female plug is made in the shape of looped portion which is extended from the eyelet members and is sleeved on the planar brims, the pulling force behind the electrical cord is not easily transmitted to the male plug and female plug by use of stretching the electrical cord in hook members of planar brims, so that the connection of male plug and female plug can not be separated by the pulling force; the above-mentioned structure is not so ideal, because the electrical cord must be more than twice folded.
In male plug or female plug having electrical cord, the connection between its plug body and electrical cord is very tight (it's even then integrated), the connecting position is not easily broken, what is more, the head bodies of male plug and female plug are large than the diameter of electrical cord.